Wet strength polymers

Abstract

The invention provides a stable polymeric additive useful for improving the wet strength of a cellulosic substrate. The additive is a water-soluble cationic thermosetting polymer incorporating a plurality of extralinear glycidyl quaternary ammonium groups. The invention also comprises a method of making such an additive.

What is claimed is: 
     
       1. A process for the production of a water soluble, cationic, thermosetting polymeric wet strength additive which comprises reacting, in an aqueous medium maintained at a temperature of 20° C. or less, an epihalohydrin and a polymer comprising a backbone formed of repeating segments at least 10% of which comprise an amine group and/or partial salts thereof substantially all of said amine groups being tertiary amine groups pendant from the polymer backbone and having a structure selected from the group consisting of ##STR10## wherein R' is selected from the group consisting of methyl and, where the nitrogen atom bears two R' groups, these together with the nitrogen can form a heterocyclic radical; 
     
     
       R" is a divalent radical and R'" is a trivalent radical; the unattached bond in each amine structure being attached directly to a carbon atom of the polymer backbone;   the ratio of epihalohydrin groups to tertiary amine groups reacted being not less than the transition ratio for the reaction conditions selected.   
     
     
       2. A process according to claim 1 in which the reaction temperature is from -5° to 15° C. 
     
     
       3. A process according to claim 1 in which the amine-containing polymer comprises at least 50 molar percent of units derived from N-methyldiallylamine. 
     
     
       4. A process according to claim 1 in which the amine-containing polymer comprises at least 40 molar percent of units derived from vinylbenzyldimethylamine. 
     
     
       5. A process according to claim 1 in which the transition ratio is less than 1.8. 
     
     
       6. A process according to claim 1 in which the epihalohydrin is epichlorohydrin. 
     
     
       7. A process for the production of a water-soluble, cationic, thermosetting polymeric wet strength additive which comprises reacting in an aqueous medium maintained, at a temperature of from -5° to 20° C., epichlorohydrin and a polymer selected from the group consisting of poly(N-methyldiallylamine), poly(vinylbenzyldimethylamine) and poly(N,N-dimethylaminoethylmethacrylate), at a pH of from 4 to 9.5 and a total solids percentage figure for the reaction mixture of from 10 to 50%, the conditions being selected such that the transition ratio for the system is less than 1.8 and the ratio of epichlorohydrin to tertiary amine groups in the reaction components is not less than the transition ratio.